Trying to run a Model Simulation on Natural gas Dew pointing of Water and Hydrocarbon. Version used is 8.7.1. of DWSIM.
On clicking the solve button, getting a response of " Use Recycle Blocks wherever it is needed".
How do we find out the required location of Recycle Block in the Process flow diagram? Any guideline is there?
Last edit: R Meenakshi sundaram 2024-05-16
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Since you did not post any flowsheet, it is difficult to say where recycle blocks are needed.
Here is the general guideline. Anytime a stream from later in the process is solved and sent back to the front of the process, you need a recycle block in the stream. There are elegant ways to draw the flowsheet and show process stream loops which make it obvious which streams need recycle blocks.
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Thanks Frank
Soe basic doubts further!
When we draw PFD/Flowsheet, we have to drag pictures of Process equipment from the available lists, place them, connnect them and give attributes. Unable to find figures/pictures of Process equipment like PCV, LCV, Joule Thomson Valve(JTV), Storage vessels with two outlets (One for Vapour and one for Liquid) in the list of pictures that surfaces on the Simulation Program. For PCV, LCV, JTV, etc., lookalike picture is Valve. Can we drag Valve, Place it and rename as PCV or LCV or JTV appropriately? Will the Simulation results be correct in such substitution?
Similarly, Tank is the closest resembling picture vessel for depicting Rich Glycol Flash Drum in Natural gas processing. Rich Glycol flash drum needs one vapour outlet and one liquid outlet. But the Tank has only one outlet. When we place tank in place of Rich Glycol Flash drum, unable to add second outlet to the tank.
How to overcome above problems?
Regards.
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sundaram: You have it correct. A Valve is just a Valve. It is the specifications you assign it that determine what it does. As for the storage tank with two (2) outlets, one for vapor and one for liquid. You are correct in using a liquid/vapour separator. After all you are only making a simulation. If it does what you want it to do great. You are not making a painting.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi Frank,
Rich TEG, emerging out from an Absorber of Natural Gas Dehydration is regenerated to get 99.6% (by weight) pure Lean TEG for Absorption. Rest 0.4% is Water. Regeneration flowsheet is enclosed. Facing many problems. Kindly go through the same and guide how to move ahead.
Regards.
Hi Frank,
Thank you very much.
We are in the model of Natural Gas Dew pointing. Water Dew point is to be controlled by Glycol Dehydration and HC dew pointing is to be done by Mechanical Refrigeration. Wet gas rate is 300,000 Cubic metres per day with 3 % (weight) free condensate and 2 % (weight) free water. Inlet T is 31.5 °C and P is 4,900,000 Pascals. Desired Dew points are -5 °C (Water) and -5 °C (HC). Required stripping gas rate is 0.218 mole/sec and TEG rate is 0.683 mole/sec. We added the flow sheet corrected and sent by you to the other two parts of Dehydration and Refrigeration which were through earlier but turned red now.
Attached the full sheet. Can you please check it up and help?
R Meenakshi sundaram
You have made on complicated flow sheet. It will take some time to think it through.
For instance, I do not understand where it begins. Usually, the feed streams are to the left on a Process Flow diagram. And the end result is on the right. I suspect the solver wants to start at the left end of the Flowsheet. You cannot start with a recycled stream. You can start with a feed and add a stream that is a recycle.
You might help yourself by looking at each piece of equipment by itself and accessing it material flow, Heat flows with temperatures and phases since you are dealing with 3 phases, Hydrocarbon, Water and Glycol. You can probably ignore quantities below 10 to the -6th as effectively zero.
Dumb computer calculates a lot without descrimination.
You also might try writing a Process Description for us and yourself. This will clarify what you have in mind.
I will continue to look. Post any updates here.
Regards
Frank R Brown III
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Prof PR Naren, Sastra University helped in solving the errors further and the latest flowsheet which is through, is enclosed herewith. This is the latest update.
Process Description is given below.
Process Description:
Natural Gas produced in a particular location has to be dispatched to consumers who are far away in tens of kilometres through trunk lines. Natural gas produced from the well has liquid free water and liquid condensate. Added to the free liquid, the Natural gas is fully saturated with water. Composition of Natural gas ranges as C1, C2, C3 and goes higher. Free liquid, Associated water and Hydrocarbon components higher than C5 are hazardous in nature in Pipeline transportation as they tempt to form hydrates while handling and moving. To avoid the probability of hydrate formation natural gas has to be dispatched without free liquid, associated water and heavy hydrocarbon. The parameters that will ensure this removal are Dew Point (Water) which has to be at least -5 Degrees C and Dew Point (HC) which has to be again at least - 5 Degrees C.
This job is done in four parts.
Part 1: Free liquid is separated by a gravity separator right in the inlet stage.
Part 2: Associated water is removed by Absorption using Triethylene Glycol (TEG) in this part which is also called the Glycol Dehydration unit.
Part 3: Rich TEG getting after absorbing the Associated water in the gas, is regenerated by heating through a series of Glycol stripping column, Glycol Reboiler, Glycol still and Glycol reflux condenser and recirculated back to Absorption column as Lean Glycol for absorption again.
Part 4: After the absorption of water, the dehydrated gas is subjected to heavy chilling in an exchanger where a mixture of chilling medium of 60% water and 40% MEG chills the natural gas to condense heavy hydrocarbons and dry the gas totally.
The warm chilling medium is cooled by a refrigerant which is kept cool enough through a refrigeration cycle involving Compressor, Air cooled condenser and Joule Thomson valve in two trains.
The dried gas is sent as Export gas.
We will move to run the same flowsheet in Dynamic state.
Thanks Frank again and Regards.
Trying to run a Model Simulation on Natural gas Dew pointing of Water and Hydrocarbon. Version used is 8.7.1. of DWSIM.
On clicking the solve button, getting a response of " Use Recycle Blocks wherever it is needed".
How do we find out the required location of Recycle Block in the Process flow diagram? Any guideline is there?
Last edit: R Meenakshi sundaram 2024-05-16
Since you did not post any flowsheet, it is difficult to say where recycle blocks are needed.
Here is the general guideline. Anytime a stream from later in the process is solved and sent back to the front of the process, you need a recycle block in the stream. There are elegant ways to draw the flowsheet and show process stream loops which make it obvious which streams need recycle blocks.
Thanks Frank
Soe basic doubts further!
When we draw PFD/Flowsheet, we have to drag pictures of Process equipment from the available lists, place them, connnect them and give attributes. Unable to find figures/pictures of Process equipment like PCV, LCV, Joule Thomson Valve(JTV), Storage vessels with two outlets (One for Vapour and one for Liquid) in the list of pictures that surfaces on the Simulation Program. For PCV, LCV, JTV, etc., lookalike picture is Valve. Can we drag Valve, Place it and rename as PCV or LCV or JTV appropriately? Will the Simulation results be correct in such substitution?
Similarly, Tank is the closest resembling picture vessel for depicting Rich Glycol Flash Drum in Natural gas processing. Rich Glycol flash drum needs one vapour outlet and one liquid outlet. But the Tank has only one outlet. When we place tank in place of Rich Glycol Flash drum, unable to add second outlet to the tank.
How to overcome above problems?
Regards.
sundaram: You have it correct. A Valve is just a Valve. It is the specifications you assign it that determine what it does. As for the storage tank with two (2) outlets, one for vapor and one for liquid. You are correct in using a liquid/vapour separator. After all you are only making a simulation. If it does what you want it to do great. You are not making a painting.
Thanks frank.
Hi Frank,
Rich TEG, emerging out from an Absorber of Natural Gas Dehydration is regenerated to get 99.6% (by weight) pure Lean TEG for Absorption. Rest 0.4% is Water. Regeneration flowsheet is enclosed. Facing many problems. Kindly go through the same and guide how to move ahead.
Regards.
Try this!
Last edit: Frank R Brown III 2024-05-30
Try this
Sorry I am having trouble posting. Bear with Me
I renamed the file copy-2.
Hi Frank,
Thank you very much.
We are in the model of Natural Gas Dew pointing. Water Dew point is to be controlled by Glycol Dehydration and HC dew pointing is to be done by Mechanical Refrigeration. Wet gas rate is 300,000 Cubic metres per day with 3 % (weight) free condensate and 2 % (weight) free water. Inlet T is 31.5 °C and P is 4,900,000 Pascals. Desired Dew points are -5 °C (Water) and -5 °C (HC). Required stripping gas rate is 0.218 mole/sec and TEG rate is 0.683 mole/sec. We added the flow sheet corrected and sent by you to the other two parts of Dehydration and Refrigeration which were through earlier but turned red now.
Attached the full sheet. Can you please check it up and help?
Regards.
R Meenakshi sundaram
You have made on complicated flow sheet. It will take some time to think it through.
For instance, I do not understand where it begins. Usually, the feed streams are to the left on a Process Flow diagram. And the end result is on the right. I suspect the solver wants to start at the left end of the Flowsheet. You cannot start with a recycled stream. You can start with a feed and add a stream that is a recycle.
You might help yourself by looking at each piece of equipment by itself and accessing it material flow, Heat flows with temperatures and phases since you are dealing with 3 phases, Hydrocarbon, Water and Glycol. You can probably ignore quantities below 10 to the -6th as effectively zero.
Dumb computer calculates a lot without descrimination.
You also might try writing a Process Description for us and yourself. This will clarify what you have in mind.
I will continue to look. Post any updates here.
Regards
Frank R Brown III
Thanks Frank,
Prof PR Naren, Sastra University helped in solving the errors further and the latest flowsheet which is through, is enclosed herewith. This is the latest update.
Process Description is given below.
Process Description:
Natural Gas produced in a particular location has to be dispatched to consumers who are far away in tens of kilometres through trunk lines. Natural gas produced from the well has liquid free water and liquid condensate. Added to the free liquid, the Natural gas is fully saturated with water. Composition of Natural gas ranges as C1, C2, C3 and goes higher. Free liquid, Associated water and Hydrocarbon components higher than C5 are hazardous in nature in Pipeline transportation as they tempt to form hydrates while handling and moving. To avoid the probability of hydrate formation natural gas has to be dispatched without free liquid, associated water and heavy hydrocarbon. The parameters that will ensure this removal are Dew Point (Water) which has to be at least -5 Degrees C and Dew Point (HC) which has to be again at least - 5 Degrees C.
This job is done in four parts.
Part 1: Free liquid is separated by a gravity separator right in the inlet stage.
Part 2: Associated water is removed by Absorption using Triethylene Glycol (TEG) in this part which is also called the Glycol Dehydration unit.
Part 3: Rich TEG getting after absorbing the Associated water in the gas, is regenerated by heating through a series of Glycol stripping column, Glycol Reboiler, Glycol still and Glycol reflux condenser and recirculated back to Absorption column as Lean Glycol for absorption again.
Part 4: After the absorption of water, the dehydrated gas is subjected to heavy chilling in an exchanger where a mixture of chilling medium of 60% water and 40% MEG chills the natural gas to condense heavy hydrocarbons and dry the gas totally.
The warm chilling medium is cooled by a refrigerant which is kept cool enough through a refrigeration cycle involving Compressor, Air cooled condenser and Joule Thomson valve in two trains.
The dried gas is sent as Export gas.
We will move to run the same flowsheet in Dynamic state.
Thanks Frank again and Regards.